A positioning system for establishing or defining the exact position of a measuring point on a surface will normally include a main station which comprises a distance meter, preferably an optical distance meter, which transmits and receives a measuring light beam in essentially the same direction, for instance an electronic distance meter (EDM) which functions to transmit and receive reflected modulated light and to make comparisons between the modulation signal of the transmitted and the received light beam, respectively. The system will also include a so-called vertical angle meter and a horizontal angle meter which function to determine the position of alignment of the distance meter with the object to be measured. The main station is set-up in the terrain and measurements are taken against setting-out staffs. The main station can either be manned by a single person or may be of the kind which locks automatically onto a prism on a setting-out staff and follows the prism as the staff is moved by the staffman. The use of a close-range measuring system for linking such a positioning system to a total principal measuring system, for instance a coordinate system, can be both effective and cost saving. By close-range measuring system is meant in the present context a system which obtains data for the starting position in an external main network and from there measures-up local points that are linked with the external network.
Situations also arise in which one and the same measuring equipment cannot be used for measuring a total area, but must be complemented with measurements taken with other equipment. When marking out an area, e.g. a plot of land, a road or highway etc., it is normal practice to place a distance meter in a central position.
Setting-out staffs or sticks are then placed in position at mutually different measuring points in the terrain, by direct measurement between the centrally placed measuring instrument at each relevant measuring point. Occasionally some of the measuring points will be concealed from view with respect to the position of the distance measuring instrument, which then involves extra work in moving the instrument and also in making additional reference measurements for the purpose of determining the exact position of these points. This is particularly troublesome in the case of measuring equipment which can be handled by a single person and the use of which equipment is thus expanded upon. In the case of equipment of this nature, the centrally positioned distance measuring instrument will align automatically on the measuring point concerned or on the prism located on the staff that has been set-out. Naturally, movement of the instrument should be avoided if at all possible.
The use of such a close-range measuring system in cooperation with a main station is also particularly advantageous for determining the external measurements of a large object, for instance a car body.